Carlos García-Delgado

Combination of biochar amendment and mycoremediation for polycyclic aromatic hydrocarbons immobilization and biodegradation in creosote-contaminated soil

Soils impregnated with creosote contain high concentrations of polycyclic aromatic hydrocarbons (PAH). To bioremediate these soils and avoid PAH spread, different bioremediation strategies were tested, based on natural attenuation, biochar application, wheat straw biostimulation, Pleurotus ostreatus mycoremediation, and the novel sequential application of biochar for 21 days and P. ostreatus 21 days more. Soil was sampled after 21 and 42 days after the remediation application. The efficiency and effectiveness of each remediation treatment were assessed according to PAH degradation and immobilization, fungal and bacterial development, soil eco-toxicity and legal considerations. Natural attenuation and biochar treatments did not achieve adequate PAH removal and soil eco-toxicity reduction. Biostimulation showed the highest bacterial development but low PAH degradation rate. Mycoremediation achieved the best PAH degradation rate and the lowest bioavailable fraction and soil eco-toxicity. This bioremediation strategy achieved PAH concentrations below Spanish legislation for contaminated soils (RD 9/2005). Sequential application of biochar and P. ostreatus was the second treatment most effective for PAH biodegradation and immobilization. However, the activity of P. ostreatus was increased by previous biochar application and PAH degradation efficiency was increased. Therefore, the combined strategy for PAH degradation have high potential to increase remediation efficiency.

Implications of polluted soil biostimulation and bioaugmentation with spent mushroom substrate (Agaricus bisporus) on the microbial community and polycyclic aromatic hydrocarbons biodegradation

Different applications of spent Agaricus bisporus substrate (SAS), a widespread agro-industrial waste, were investigated with respect to the remediation of a historically polluted soil with Polycyclic Aromatic Hydrocarbons (PAH). In one treatment, the waste was sterilized (SSAS) prior to its application in order to assess its ability to biostimulate, as an organic amendment, the resident soil microbiota and ensuing contaminant degradation. For the other treatments, two bioaugmentation approaches were investigated; the first involved the use of the waste itself and thus implied the application of A. bisporus and the inherent microbiota of the waste. In the second treatment, SAS was sterilized and inoculated again with the fungus to assess its ability to act as a fungal carrier. All these treatments were compared with natural attenuation in terms of their impact on soil heterotrophic and PAH-degrading bacteria, fungal growth, biodiversity of soil microbiota and ability to affect PAH bioavailability and ensuing degradation and detoxification. Results clearly showed that historically PAH contaminated soil was not amenable to natural attenuation. Conversely, the addition of sterilized spent A. bisporus substrate to the soil stimulated resident soil bacteria with ensuing high removals of 3-ring PAH. Both augmentation treatments were more effective in removing highly condensed PAH, some of which known to possess a significant carcinogenic activity. Regardless of the mode of application, the present results strongly support the adequacy of SAS for environmental remediation purposes and open the way to an attractive recycling option of this waste.

Bioremediation of multi-polluted soil by spent mushroom (Agaricus bisporus) substrate: Polycyclic aromatic hydrocarbons degradation and Pb availability

This study investigates the effect of three spent Agaricus bisporus substrate (SAS) application methods on bioremediation of soil multi-polluted with Pb and PAH from close to a shooting range with respect natural attenuation (SM). The remediation treatments involve (i) use of sterilized SAS to biostimulate the inherent soil microbiota (SSAS) and two bioaugmentation possibilities (ii) its use without previous treatment to inoculate A. bisporus and inherent microbiota (SAS) or (iii) SAS sterilization and further A. bisporus re-inoculation (Abisp). The efficiency of each bioremediation microcosm was evaluated by: fungal activity, heterotrophic and PAH-degrading bacterial population, PAH removal, Pb mobility and soil eco-toxicity. Biostimulation of the native soil microbiology (SSAS) achieved similar levels of PAH biodegradation as SM and poor soil detoxification. Bioaugmented microcosms produced higher PAH removal and eco-toxicity reduction via different routes. SAS increased the PAH-degrading bacterial population, but lowered fungal activity. Abisp was a good inoculum carrier for A. bisporus exhibiting high levels of ligninolytic activity, the total and PAH-degrading bacteria population increased with incubation time. The three SAS applications produced slight Pb mobilization (<0.3%). SAS sterilization and further A. bisporus re-inoculation (Abisp) proved the best application method to remove PAH, mainly BaP, and detoxify the multi-polluted soil.

Cadmium and lead bioavailability and their effects on polycyclic aromatic hydrocarbons biodegradation by spent mushroom substrate

Bioremediation of mixed metal–organic soil pollution constitutes a difficult task in different ecosystems all around the world. The aims of this work are to determine the capacity of two spent mushroom substrates (Agaricus bisporus and Pleurotus ostreatus) to immobilize Cd and Pb, to assess the effect of these metals on laccase activity, and to determine the potential of spent A. bisporus substrate to biodegrade four polycyclic aromatic hydrocarbons (PAH): fluorene, phenanthrene, anthracene, and pyrene, when those toxic heavy metals Cd and Pb are present. According to adsorption isotherms, spent P. ostreatus and A. bisporus substrates showed a high Pb and Cd adsorption capacity. Pb and Cd interactions with crude laccase enzyme extracts from spent P. ostreatus and A. bisporus substrates showed Cd and Pb enzyme inhibition; however, laccase activity of A. bisporus presented lower inhibition. Spent A. bisporus substrate polluted with PAH and Cd or Pb was able to biodegrade PAH, although both metals decrease the biodegradation rate. Spent A. bisporus substrate contained a microbiological consortium able to oxidize PAH with high ionization potential. Cd and Pb were immobilized during the bioremediation process by spent A. bisporus substrate. Consequently, spent A. bisporus substrate was adequate as a multi-polluted soil bioremediator.

Evaluation of Fe-N,N′-Bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetate (HBED/Fe3+) as Fe carrier for soybean (Glycine max) plants grown in calcareous soil

AimsThe efficacy of N,N′-bis(2-hydroxybenzyl)ethylenediamine-N,N′-diacetic acid (HBED) as an Fe source in plant nutrition for soybean (Glycine max) plants grown in calcareous soil under controlled conditions was studied.MethodsThe ability of ethylenediamine-N,N′-bis(o-hydroxyphenylacetic) acid (o,oEDDHA/57Fe3+) and HBED/57Fe3+ at increasing concentrations and the long lasting effect were evaluated. In addition, iron nutrition was studied considering the Fe uptake from the chelates prepared with the isotope 57Fe. Further, the SPAD index, total Fe and 57Fe content in plant were analyzed and soluble and available 57Fe fractions in soil were determined over time.ResultsDoses experiment indicated that a higher concentration of HBED/57Fe3+ as compared to o,oEDDHA/57Fe3+ is necessary for obtaining the same 57Fe absorption by the plant; however, these differences were found to be lower in the second sampling time as compared to the first one. This long lasting effect of HBED/Fe3+ was corroborated in the long term experiment. Moreover, it was found that the load of Fe in the pods was higher when using HBED/57Fe3+ than when o,oEDDHA/57Fe3+ was used. The soil extract analysis for each sampling time indicated that HBED/57Fe3+ presented a higher stability in soil than o,oEDDHA/57Fe3+ over time.ConclusionThe HBED/Fe3+ could be a long lasting alternative to EDDHA/Fe3+ for correcting the iron chlorosis of dicotyledonous plants grown on calcareous soils.

Methodology for Polycyclic Aromatic Hydrocarbons Extraction from Either Fresh or Dry Spent Mushroom Compost and Quantification by High-Performance Liquid Chromatography–Photodiode Array Detection

Polycyclic aromatic hydrocarbons (PAH) are a family of compounds classified as persistent organic pollutants, which are hazardous for environmental and human health. White rot fungi are organisms that are able to remediate PAH from polluted soils. Spent mushroom compost (SMC) is employed for soil bioremediation and environmental research. In this study, four solvents [acetone/dichloromethane (CH2Cl2) 1:1 mixture; acetone/hexane 1:1 mixture; methanol, and acetone], which are among those already used for PAH solvents, were chosen to be combined with two extraction procedures (ultrasound and orbital shaking). All extracted PAH were quantified by high-performance liquid chromatography (HPLC)–photodiode array detection (PDA). Certified soil CRM141, containing 16 PAH included in the U.S. Environmental Protection Agency priority list, was used for methodology validation. The orbital shaking procedure was selected because all detected and quantified PAH were within the CRM141 prediction interval, and there was less variability for all checked solvents than in the ultrasonic procedure. Once the orbital shaking methodology was selected, fluorene, phenanthrene, anthracene, and pyrene standards were added to fresh (60% moisture content) and dry SMC. The orbital shaking procedure was carried out over 24 h to avoid PAH degradation, and 1 month later to provide PAH interaction with solid matrix in this period of time. The PAH orbital shaking extraction over dry SMC showed large recovery percentages for all tested solvents. The PAH extracted from fresh SMC showed biodegradation after 24 h. Acetone/CH2Cl2 (1:1), methanol, and acetone solvents employed over fresh SMC recovered less than solvents over dry SMC. Acetone/hexane (1:1) recovered more than 80% and did not show any decrease in recovery over fresh SMC. Results indicate that it is not necessary to include a drying step prior to PAH extraction if the acetone/hexane (1:1) solvent mixture is employed. The recommended methodology for PAH extraction includes orbital shaking of fresh compost with acetone/hexane (1:1) solvent mixture and quantification by HPLC-PDA.

Total and fraction content of elements in volcanic soil: Natural or anthropogenic derivation

Soil element composition derives from parent material disaggregation during pedogenesis and weathering processes but also by anthropogenic inputs. Elements are present in soils in different chemical forms that affect their availability and mobility. The aim of the study was to evaluate the main derivation, natural or anthropogenic, of elements in the soils of the Vesuvius National Park (a natural environment strongly affected by human impacts). Besides, the effects of age of the lava from which soils derive, different vegetation covers, traffic fluxes along the two roads connecting the Vesuvius crater and altitudes of the sites on the pseudo-total element concentrations and on their contents in different fraction of soil were investigated. To reach the aims, BCR (Bureau Commun de Référence) sequential extraction was performed in order to determine the distribution of elements into: acid-soluble, reducible, oxidizable and residual fractions. The relationship between the main environmental media and distribution of elements was discussed using non-metric multidimensional scaling (NMDS). The findings showed that, with the exception of Cd, Cu, Pb and Zn that would seem to derive also from human activities, the other investigated elements (Al, As, B, Ba, Ca, Cd, Cr, Cu, Fe, K, La, Mg, Mn, Na, Ni, P, Pb, Si, Ti, V, W and Zn) mainly had a natural derivation. Among the investigated elements, only Cd could represent a potential high risk for the studied andosols. The highest element accumulations in the soils at low altitude could be attributable to an integrated effect of plant cover, vicinity of downtowns and traffic flux. The acid-soluble fraction of elements appeared more linked to lava age; the reducible and oxidizable ones to plant cover; the residual one to the chemical composition of the parent material that gave origin to the soils.

Are physico-chemical soil characteristics key factors to select the polycyclic aromatic hydrocarbons extraction procedure?

ABSTRACT The aim of this work was to assess the impact of soil characteristics and constituents in the total extraction of hydrophobic organic pollutants, such as polycyclic aromatic hydrocarbons (PAH), in real polluted soil samples from different sources. Soil samples were obtained from a wood creosote treatment plant, in the vicinity of a metallurgy industry and coal thermal power stations. Soils showed a wide diversity of textures, organic matter (OM) and CaCO3 content, pH and electrical conductivity to assure representativeness of multiple situations. Two extraction procedures with soft (solid–liquid extraction, SLE) and intense (pressurised liquid extraction, PLE) extraction power were used to determine the total concentration of PAH in soils. Results obtained showed that soil properties affect the effectiveness of the extraction procedures tested. The validation of PAH extraction procedure with a reference soil did not confirm that the procedure was adequate for all kinds of soil. Results showed that OM content and clay were the main soil characteristics that should be taken into account to select the most adequate PAH extraction procedure for any given polluted soil.

Soil element fractions affect phytotoxicity, microbial biomass and activity in volcanic areas

Soil quality is strongly affected by microbial biomass that is involved in organic matter mineralization and the supply of nutrients to plants. The effects of trace elements on soil microbial biomass and activity are still controversial, and the contents of the elements in different forms, more than the total amounts, may affect soil microbial community. Volcanic soils are peculiar environments because of their chemical characteristics. Therefore, the aims of this research were to evaluate in volcanic soils: i) the elemental composition; ii) the elemental availability; and iii) the effects of elemental fractions on soil microbial biomass and activity. In order to reach the aims, the BCR sequential extraction method was applied in order to separate 22 elements in different soil fractions: acid soluble, reducible, oxidisable and residual. The studied biological parameters were: microbial and fungal biomasses, soil respiration, metabolic quotient, coefficient of endogenous mineralization, dehydrogenase and hydrolase activities, and phytotoxicity. Among the investigated elements, Al, B, Ba, Ca, Cr, Fe, K, Mg, Mn, Na, Ni, Ti, V and Zn were scarcely available; Cd appeared to be the most ready available element; Zn was mainly present in the acid soluble and in the residual fractions. Microbial biomass and activity appeared to be mainly affected by the reducible and oxidasable fractions of the investigated elements more than the acid soluble or residual ones. With the exception of La and V, the elemental content in the various fractions would seem to stimulate the microbial biomass and activity. Finally, the investigated volcanic soils showed phytotoxic properties.

Purification of polluted water with spent mushroom (Agaricus bisporus) substrate: from agricultural waste to biosorbent of phenanthrene, Cd and Pb

ABSTRACT The present research was aimed to (i) report the recycling of spent A. bisporus substrate (SAS) to remove heavy metals (Cd and Pb) and phenanthrene (Phe) from polluted water and (ii) assess the possibility to use the treated water for irrigation. Batch experiments were carried out to assess, firstly, the effect of interaction time between pollutants with SAS and, secondly, the pH of the polluted water. Then a biofilter was designed by using pressurized glass columns. Chemical parameters such as pH, electrical conductivity and content of Pb, Cd, Phe, nutrients (NPK) and Cl− were determined. Equilibrium for contaminants was quickly reached (1–2 h). The pH of the polluted water was the key factor for pollutants’ adsorption. The polluted water’s pH was increased after biofilter interaction. Phe was not detected in any fraction. Pb and Cd sorption rates were higher than 99%. The pollutant concentrations were within the permitted range to be used for agriculture purposes. Purified water showed significant concentrations of NPK, indicating its potential use as fertilizer. The SAS shows potential to be used as Phe, Pb and Cd biosorbent and the resulting treated water can be used for irrigation according to pollutant contents and agronomical evaluation.